2011 Equonix the heat for the interior works some times and sometimes not. Engine is hot but just get cold air from vents, in auto or manual. It will work fine then shut car off and back 15 mins later and no heat. It will not work cold engine drive for 20 mins no heat entire time then drive again 30 mins later and heats fine. No consistancey when it fails. Had appt scheduled and it was working fine after talking to service dept decide to cancel and problem has continued going to tkae it for service and hope its not working when its there. Anyone had this problem or have any ideas?